Field of the Invention
The invention relates to friction welding apparatus.
In particular the invention concerns a linear friction welding machine. That is a machine for welding together two workpieces which are caused to reciprocate relatively in a rectilinear movement while being pressed together.
As the workpieces are moved one relative to the other while at the same time being pressed together with a substantial force, which may be several tonnes, the forces exerted on and reacted by the workpiece holders are correspondingly massive. It follows that because various reciprocating parts of the apparatus have to be massive to withstand the forces involved a considerable amount of work is done in each cycle of the machine first to accelerate the moving parts, then to decelerate the parts, reverse the direction of movement and to repeat the process. Although a substantial proportion of the work input is converted into heat at the weld joint interface, and some is lost to internal friction, the remainder is expended in cyclically creating and then destroying machine momentum.